title: Respiratory pulse pressure variation fails to predict fluid responsiveness in acute respiratory distress syndrome.
abstract: BACKGROUND
  Fluid responsiveness prediction is of utmost interest during acute respiratory distress syndrome (ARDS), but the performance of respiratory pulse pressure variation (ΔRESPPP) has scarcely been reported. In patients with ARDS, the pathophysiology of ΔRESPPP may differ from that of healthy lungs because of low tidal volume (Vt), high respiratory rate, decreased lung and sometimes chest wall compliance, which increase alveolar and/or pleural pressure. We aimed to assess ΔRESPPP in a large ARDS population.
  
  
  METHODS
  Our study population of nonarrhythmic ARDS patients without inspiratory effort were considered responders if their cardiac output increased by >10% after 500-ml volume expansion.
  
  
  RESULTS
  Among the 65 included patients (26 responders), the area under the receiver-operating curve (AUC) for ΔRESPPP was 0.75 (95% confidence interval (CI95): 0.62 to 0.85), and a best cutoff of 5% yielded positive and negative likelihood ratios of 4.8 (CI95: 3.6 to 6.2) and 0.32 (CI95: 0.1 to 0.8), respectively. Adjusting ΔRESPPP for Vt, airway driving pressure or respiratory variations in pulmonary artery occlusion pressure (ΔPAOP), a surrogate for pleural pressure variations, in 33 Swan-Ganz catheter carriers did not markedly improve its predictive performance. In patients with ΔPAOP above its median value (4 mmHg), AUC for ΔRESPPP was 1 (CI95: 0.73 to 1) as compared with 0.79 (CI95: 0.52 to 0.94) otherwise (P = 0.07). A 300-ml volume expansion induced a ≥ 2 mmHg increase of central venous pressure, suggesting a change in cardiac preload, in 40 patients, but none of the 28 of 40 nonresponders responded to an additional 200-ml volume expansion.
  
  
  CONCLUSIONS
  During protective mechanical ventilation for early ARDS, partly because of insufficient changes in pleural pressure, ΔRESPPP performance was poor. Careful fluid challenges may be a safe alternative.
authors.affiliation: Service de réanimation médicale et maladies infectieuses, Hôpital Bichat- Claude Bernard, Assistance Publique des Hôpitaux de Paris, 18 rue Henri Huchard, F-75018 Paris, France.
authors.forename: Karim
authors.initials: K
authors.lastname: Lakhal
authors.forename: Stephan
authors.initials: S
authors.lastname: Ehrmann
authors.forename: Dalila
authors.initials: D
authors.lastname: Benzekri-Lefèvre
authors.forename: Isabelle
authors.initials: I
authors.lastname: Runge
authors.forename: Annick
authors.initials: A
authors.lastname: Legras
authors.forename: Pierre-François
authors.initials: PF
authors.lastname: Dequin
authors.forename: Emmanuelle
authors.initials: E
authors.lastname: Mercier
authors.forename: Michel
authors.initials: M
authors.lastname: Wolff
authors.forename: Bernard
authors.initials: B
authors.lastname: Régnier
authors.forename: Thierry
authors.initials: T
authors.lastname: Boulain
mesh_terms: D000368:Aged; D001794:Blood Pressure / Q000502:physiology*; D002302:Cardiac Output; D005260:Female; D005440:Fluid Therapy; D006801:Humans; D008297:Male; D008875:Middle Aged; D011175:Positive-Pressure Respiration; D012128:Respiratory Distress Syndrome / Q000503:physiopathology* / Q000628:therapy*; D015656:Respiratory Mechanics / Q000502:physiology*; D013990:Tidal Volume; D016896:Treatment Outcome